diff --git a/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs b/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs
index 7c44f4e..871127a 100644
--- a/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs
+++ b/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs
@@ -375,7 +375,8 @@ namespace CryptoExchange.Net.Testing.Comparers
                 }
                 else if (objectValue is DateTime time)
                 {
-                    if (time != DateTimeConverter.ParseFromString(jsonValue.Value<string>()!))
+                    var jsonStr = jsonValue.Value<string>()!;
+                    if (!string.IsNullOrEmpty(jsonStr) && time != DateTimeConverter.ParseFromString(jsonStr))
                         throw new Exception($"{method}: {property} not equal: {jsonValue.Value<string>()} vs {time}");
                 }
                 else if (objectValue is bool bl)
diff --git a/CryptoExchange.Net/Testing/TestHelpers.cs b/CryptoExchange.Net/Testing/TestHelpers.cs
index 59d1e7a..0f91d44 100644
--- a/CryptoExchange.Net/Testing/TestHelpers.cs
+++ b/CryptoExchange.Net/Testing/TestHelpers.cs
@@ -173,17 +173,20 @@ namespace CryptoExchange.Net.Testing
 
             foreach (var clientInterface in clientInterfaces)
             {
-                var implementation = assembly.GetTypes().Single(t => clientInterface.IsAssignableFrom(t) && t != clientInterface);
-                int methods = 0;
-                foreach (var method in implementation.GetMethods().Where(m => implementationTypes.IsAssignableFrom(m.ReturnType)))
+                var implementations = assembly.GetTypes().Where(t => clientInterface.IsAssignableFrom(t) && t != clientInterface);
+                foreach (var implementation in implementations)
                 {
-                    var interfaceMethod = clientInterface.GetMethod(method.Name, method.GetParameters().Select(p => p.ParameterType).ToArray());
-                    if (interfaceMethod == null)
-                        throw new Exception($"Missing interface for method {method.Name} in {implementation.Name} implementing interface {clientInterface.Name}");
-                    methods++;
-                }
+                    int methods = 0;
+                    foreach (var method in implementation.GetMethods().Where(m => implementationTypes.IsAssignableFrom(m.ReturnType)))
+                    {
+                        var interfaceMethod = clientInterface.GetMethod(method.Name, method.GetParameters().Select(p => p.ParameterType).ToArray());
+                        if (interfaceMethod == null)
+                            throw new Exception($"Missing interface for method {method.Name} in {implementation.Name} implementing interface {clientInterface.Name}");
+                        methods++;
+                    }
 
-                Debug.WriteLine($"{clientInterface.Name} {methods} methods validated");
+                    Debug.WriteLine($"{clientInterface.Name} {methods} methods validated");
+                }
             }
         }
     }